function change_link()
{

		 if(document.catalog_items.pen_camera[0].checked){
		   document.getElementById("div_1gb").style.display
	= "block";
		   document.getElementById("div_2gb").style.display
	= "none" ;
		   document.getElementById("div_4gb").style.display
	= "none" ;
		   document.getElementById("div_8gb").style.display
	= "none" ;
		 }
		 else if (document.catalog_items.pen_camera[1].checked){
		   document.getElementById("div_1gb").style.display
	= "none";
		   document.getElementById("div_2gb").style.display
	=  "block";
		   document.getElementById("div_4gb").style.display
	=  "none";
		   document.getElementById("div_8gb").style.display
	= "none" ;
     }
		 else if (document.catalog_items.pen_camera[2].checked){
		   document.getElementById("div_1gb").style.display
	= "none";
		   document.getElementById("div_2gb").style.display
	=  "none";
		   document.getElementById("div_4gb").style.display
	=  "block";
		   document.getElementById("div_8gb").style.display
	= "none" ;
     }

		 else if (document.catalog_items.pen_camera[3].checked){
		   document.getElementById("div_1gb").style.display
	= "none";
		   document.getElementById("div_2gb").style.display
	=  "none";
		   document.getElementById("div_4gb").style.display
	=  "none";
		   document.getElementById("div_8gb").style.display
	= "block" ;
     }

}